The present invention pertains to granulation processes, more specifically to a process for forming a granulate which comprises between about 75 weight percent and about 99 weight percent of riboflavin and between about 1 weight percent and about 25 weight percent of a binder. Moreover, the present invention pertains to a method of making a riboflavin-containing granulate via rotary fluid bed granulation.
Riboflavin is available as a fine powder of various purities (90 to 100 percent) comprised of riboflavin crystals 0.5 to 2 microns wide and 1 to 25 microns long. This powder is clingy, dusty and electrostatic. The powder sticks to and fouls processing equipment with which it comes into contact. Furthermore, the powder tends to bridge and clump during handling. There can be significant losses due to a buildup of riboflavin powder on the processing equipment utilized in the food and feed, and pharmaceutical industries. In addition, substantial labor must be expended to remove adhering riboflavin powder from the equipment.
In the feed industry, riboflavin powder can be made more manageable (i.e., non-dusty, non-adherent, and free-flowing), by spray drying an aqueous slurry of approximately 25% weight percent riboflavin, approximately 25% weight percent filler, and about 50% water. The filler is generally any water-soluble starch, corn syrup, dextrin, or pregelatinized starch. The filler improves the performance of the powder by encapsulating the riboflavin. However, this method is not suitable for the food and pharmaceutical industries because the pharmaceutical and food industries require high riboflavin concentrations, i.e., riboflavin concentrations of between 90 percent by weight and 100 percent by weight.
Prior to this invention, in the pharmaceutical and food industries, concentrated riboflavin powders (i.e., 90 to 100 weight percent) have been used in powder form. However, as noted above, this powder presents flowability, handling, and processing problems. The method of the present invention enables the production of a 90 to 100 weight percent riboflavin product which has heretofore unachieved flowability characteristics.
Related art of which the inventors are aware is: U.S. Pat. No. 4,868,180 (as well as the European counterpart application 0,219,276): K. W. Olsen, "Recent Advances in Fluid Bed Agglomeration and Coating Technology" , Plant/Operations Progress, Vol. 4, No. 3, pp. 135-138, July 1985; U.S. Pat. No. 3,962,384; and U.S. Pat. No. 4,486,435. None of this art discloses the use of a rotary fluid bed device for the granulation of riboflavin.
The '384 and '435 patents are directed at compositions which have a binder present in an amount around 50 weight percent. The use of large amounts of binder (i.e., amounts greater than 25 weight percent, based on total dry product weight) enables the complete granulation of the vitamin B particles, whereas complete granulation (i.e., less than 10 weight percent ungranulated vitamin crystals) is much more difficult to achieve if less than 25 weight percent binder is utilized.
The Olsen article describes the operation of a rotary granulator/coater, but the Olsen article nowhere mentions the use of such a device for the granulation of a riboflavin product. When using conventional fluid bed and spray drying operations, it has been found that if the mixture being granulated contains a proportionally large amount of riboflavin (i.e., 50 weight percent, or more), material adheres to the surfaces of the equipment, producing low product yields, and requiring significant effort to remove the adhering material from the equipment, unless special and unusual care is taken to minimize the adherence of riboflavin by mechanical mixing or exceptionally long cycle times (which renders the process cumbersome and uneconomical). The inventor of the present invention has surprisingly found that a rotary fluid bed granulator can granulate a riboflavin product comprising at least 75 weight percent riboflavin while obtaining very high yields, and without having significant amounts of material adhering to the surfaces of the equipment. Furthermore, it has surprisingly been found that the granulation is substantially complete (i.e., very few ungranulated riboflavin crystals remain in the product produced) within an economical cycle time. In contrast, the Olsen article nowhere refers to vitamin products, not to mention riboflavin products comprising riboflavin in an amount of at least 75 weight percent.
U.S. Pat. No. 4,868,180 describes a 90-99% vitamin B granulate which is made by conventional fluid bed granulation, followed by pulverizing the resulting granulate in a Fitz mill. The '180 powder nowhere refers to rotary fluid bed granulation. The '180 patent nowhere refers to the product yield. The '180 patent nowhere states that the process produces a product which is completely granulated (i.e., at least 90 weight percent granulated). In contrast to the '180 patent, the inventors of the present invention have unexpectedly found that even if the amount of binder is 25 weight percent or less, at least 90 weight percent of the riboflavin powder can be granulated via rotary fluid bed granulation. In other words, the resulting level of ungranulated pure riboflavin is, at most, only 10%. Furthermore, the inventors have unexpectedly found that product yield is very high (generally from about 97 percent to about 99 percent, based on amount of riboflavin added) when a rotary fluid bed granulator is utilized. Furthermore, the process of the present invention does not require the use of any sort of degranulation or deagglomeration of large granules or agglomerates, unlike the process described in the '180 patent, which requires a Fitz milling step. It has been unexpectedly found that in the process of the present invention a substantially fully granulated 75-plus weight percent riboflavin product can be produced via rotary fluid bed granulation, with a product yield of at least 98 weight percent, without any "degranulation" or "deagglomeration" step (e.g., milling, screening, etc.).